1. Field of the Invention
The present invention relates to an ultrasonic flowmeter and a gas flowmeter using the same, particularly, to an ultrasonic flowmeter for measuring the flow rate of a gas, a liquid, and the like by using an ultrasonic sensor and a gas flowmeter using the same.
2. Description of the Related Art
FIG. 8 shows a conventional ultrasonic flowmeter. An ultrasonic flowmeter 1 shown in FIG. 8 includes a fluid duct 2, and ultrasonic sensors 3 and 4 provided on the inner wall of the fluid duct 2. The ultrasonic sensors 3 and 4 are disposed opposing each other in a direction inclined by a predetermined angle with respect to a line perpendicular to the path of flow in the fluid duct 2. Each of the ultrasonic sensors 3 and 4 serves for generating and receiving ultrasonic waves.
In the thus configured ultrasonic flowmeter 1, the ultrasonic sensor 3 is located upstream and the ultrasonic sensor 4 is located downstream of a gas G which flows in the fluid duct 2 at a certain speed.
The ultrasonic sensors 3 and 4 simultaneously generate pulsed ultrasonic waves A and B, respectively, which are received by the ultrasonic sensors 4 and 3, respectively. In this case, time Ta taken for the ultrasonic wave A to be transmitted from the ultrasonic sensor 3 to the ultrasonic sensor 4 is shorter than time Tb taken for the ultrasonic wave B to be transmitted from the ultrasonic sensor 4 to the ultrasonic sensor 3, because the ultrasonic wave A follows the stream of the gas G while the ultrasonic wave B is against the stream. The difference between the times Ta and Tb is proportional to the speed of flow of the gas G.
Therefore, by detecting the difference between the times Ta and Tb, the speed of flow of the gas G can be measured, and when the cross-sectional area of the fluid duct 2 is known, the flow rate of the gas G can be measured with the speed of flow thereof.
A problem in the conventional ultrasonic flowmeter 1 is that a reduction in cost has not been possible because two ultrasonic sensors are required. Because of the two ultrasonic sensors being required, an additional controlling process is required so as to make the characteristics of the two ultrasonic sensors uniform, since the variation in characteristics between the two ultrasonic sensors deteriorates the measuring accuracy of the flowmeter. Another process is additionally required for selecting ultrasonic sensors having uniform characteristics, thereby preventing a reduction in cost.
Accordingly, it is an object of the present invention to provide an ultrasonic flowmeter and a gas flowmeter using the same in which a problem caused by variations in characteristics of ultrasonic sensors is solved, whereby a reduction in cost is possible.
To this end, according to the present invention, an ultrasonic flowmeter comprises a loop flow-path, an ultrasonic sensor having two opposing surfaces for transmission and reception respectively which is provided in a part of the loop flow-path, and an incoming flow-path and an outgoing flow-path which are connected to the loop flow-path. The ultrasonic sensor is disposed so that ultrasonic waves to be transmitted and received have vector components in the direction of path in the loop flow-path.
According to the present invention, in an ultrasonic flowmeter the ultrasonic sensor blocks the loop flow-path.
According to the present invention, the ultrasonic sensor further comprising two ultrasonic sensor elements, wherein each of said ultrasonic sensor elements transmits and receives the ultrasonic waves on one surface thereof, and said two ultrasonic sensor elements are joined to each other on another surface thereof.
According to the present invention, a gas flowmeter comprises any one of the above ultrasonic flowmeters.
Manufacturing cost of the ultrasonic flowmeter and the gas flowmeter using the same thus configured according to the present invention can be reduced.